問題說明
最近的幾臺機器在同一天的不同時段都出現以下警告信息:
Mar 26 20:55:03 host1 kernel: WARNING: at fs/xfs/xfs_aops.c:1045 xfs_vm_releasepage+0xcb/0x100 [xfs]()
Mar 26 20:55:03 host1 kernel: Modules linked in: nf_conntrack_ipv4 nf_defrag_ipv4 xt_conntrack nf_conntrack iptable_filter ip_tables ebtable_filter ebtables ip6table_
filter ip6_tables devlink bridge stp llc xt_multiport sunrpc dm_mirror dm_region_hash dm_log dm_mod intel_powerclamp coretemp intel_rapl iosf_mbi kvm_intel kvm irqbypa
ss crc32_pclmul ghash_clmulni_intel aesni_intel lrw gf128mul glue_helper ablk_helper cryptd iTCO_wdt iTCO_vendor_support dcdbas ipmi_devintf ipmi_si sg pcspkr ipmi_msg
handler shpchp i2c_i801 lpc_ich nfit libnvdimm acpi_power_meter kgwttm(OE) xfs libcrc32c sd_mod crc_t10dif crct10dif_generic crct10dif_pclmul crct10dif_common crc32c_i
ntel mgag200 drm_kms_helper igb syscopyarea sysfillrect sysimgblt ptp fb_sys_fops ttm pps_core dca ahci drm i2c_algo_bit libahci megaraid_sas i2c_core libata
Mar 26 20:55:03 host1 kernel: fjes [last unloaded: nf_defrag_ipv4]
Mar 26 20:55:03 host1 kernel: CPU: 10 PID: 224 Comm: kswapd0 Tainted: G OE ------------ 3.10.0-514.21.2.el7.x86_64 #1
Mar 26 20:55:03 host1 kernel: Hardware name: Dell Inc. PowerEdge R640/0W23H8, BIOS 1.3.7 02/08/2018
Mar 26 20:55:03 host1 kernel: 0000000000000000 00000000e02a0d05 ffff88103c7ebaa0 ffffffff81687073
Mar 26 20:55:03 host1 kernel: ffff88103c7ebad8 ffffffff81085cb0 ffffea0000687620 ffffea0000687600
Mar 26 20:55:03 host1 kernel: ffff88004a71daf8 ffff88103c7ebda0 ffffea0000687600 ffff88103c7ebae8
Mar 26 20:55:03 host1 kernel: Call Trace:
Mar 26 20:55:03 host1 kernel: [<ffffffff81687073>] dump_stack+0x19/0x1b
Mar 26 20:55:03 host1 kernel: [<ffffffff81085cb0>] warn_slowpath_common+0x70/0xb0
Mar 26 20:55:03 host1 kernel: [<ffffffff81085dfa>] warn_slowpath_null+0x1a/0x20
Mar 26 20:55:03 host1 kernel: [<ffffffffa038bfdb>] xfs_vm_releasepage+0xcb/0x100 [xfs]
Mar 26 20:55:03 host1 kernel: [<ffffffff81180b22>] try_to_release_page+0x32/0x50
Mar 26 20:55:03 host1 kernel: [<ffffffff81196ad6>] shrink_active_list+0x3d6/0x3e0
Mar 26 20:55:03 host1 kernel: [<ffffffff81196ed1>] shrink_lruvec+0x3f1/0x770
Mar 26 20:55:03 host1 kernel: [<ffffffff811972c6>] shrink_zone+0x76/0x1a0
Mar 26 20:55:03 host1 kernel: [<ffffffff8119857c>] balance_pgdat+0x48c/0x5e0
Mar 26 20:55:03 host1 kernel: [<ffffffff81198843>] kswapd+0x173/0x450
Mar 26 20:55:03 host1 kernel: [<ffffffff810b1b20>] ? wake_up_atomic_t+0x30/0x30
Mar 26 20:55:03 host1 kernel: [<ffffffff811986d0>] ? balance_pgdat+0x5e0/0x5e0
Mar 26 20:55:03 host1 kernel: [<ffffffff810b0a4f>] kthread+0xcf/0xe0
Mar 26 20:55:03 host1 kernel: [<ffffffff810b0980>] ? kthread_create_on_node+0x140/0x140
Mar 26 20:55:03 host1 kernel: [<ffffffff81697698>] ret_from_fork+0x58/0x90
Mar 26 20:55:03 host1 kernel: [<ffffffff810b0980>] ? kthread_create_on_node+0x140/0x140
Mar 26 20:55:03 host1 kernel: ---[ end trace 24823c5c7a1ea2be ]---
這幾臺機器的 kernel 及應用程序等崩潰信息由 abrtd 服務接管, 可以通過 abrt-cli 查看概要信息:
# abrt-cli list --since 1547518209
id 2181dce8f72761585cb6a904dbff1806c1315c27
reason: WARNING: at fs/xfs/xfs_aops.c:1045 xfs_vm_releasepage+0xcb/0x100 [xfs]()
time: Sat 23 Mar 2019 08:30:45 PM CST
cmdline: BOOT_IMAGE=/boot/vmlinuz-3.10.0-514.16.1.el7.x86_64 root=/dev/sda1 ro crashkernel=auto net.ifnames=0 biosdevname=0
package: kernel
uid: 0 (root)
count: 1
Directory: /var/spool/abrt/oops-2019-03-23-20:30:45-163925-0
內核版本如下:
Centos7
Linux host1 3.10.0-514.21.2.el7.x86_64
分析處理
紅帽知識庫
參考紅帽知識庫文檔, xfs 的這類警告信息在 xfs 模塊遍歷代碼路徑的時候會打印該信息, 不影響主機使用. 可升級內核到 kernel-3.10.0-693.el7 版本避免該警告信息, 詳細參見: redhat-access-2893711
Root Cause:
The messages were informational and they do not affect the system in a negative manner. They are seen because the XFS module is traversing through XFS code path.
代碼分析
紅帽知識庫中并未提到內存回收的相關信息, 不過從堆棧信息來看, 像是因為內核回收內存而引起的, 查看對應時間點的內存使用情況如下所示:
04:30:01 PM kbmemfree kbmemused %memused kbbuffers kbcached kbcommit %commit kbactive kbinact kbdirty
......
08:40:01 PM 513940 130976220 99.61 876 104616380 28610584 21.76 92439660 34840920 524
08:50:01 PM 479896 131010264 99.64 876 104666496 28557292 21.72 92513872 34804240 400
09:00:01 PM 455948 131034212 99.65 876 104675712 28588852 21.74 92418724 34926132 572
09:10:01 PM 556980 130933180 99.58 876 104610352 28552656 21.71 94287212 32983892 900
# sysctl vm.min_free_kbytes
vm.min_free_kbytes = 90112
20:50 到 21:00 之間的可用內存并沒有增加, 這意味著系統可能沒有做內存回收操作, 我們按照 kernel 日志的堆棧信息來看函數的調用關系:
shrink_active_list -> try_to_release_page -> xfs_vm_releasepage
//source/mm/filemap.c
3225 int try_to_release_page(struct page *page, gfp_t gfp_mask)
3226 {
3227 struct address_space * const mapping = page->mapping;
......
3233 if (mapping && mapping->a_ops->releasepage)
3234 return mapping->a_ops->releasepage(page, gfp_mask); xfs_vm_releasepage
3235 return try_to_free_buffers(page);
3236 }
//source/fs/xfs/xfs_aops.c
1034 STATIC int
1035 xfs_vm_releasepage(
1036 struct page *page,
1037 gfp_t gfp_mask)
1038 {
1039 int delalloc, unwritten;
1040
1041 trace_xfs_releasepage(page->mapping->host, page, 0, 0);
1042
1043 xfs_count_page_state(page, &delalloc, &unwritten);
1044
1045 if (WARN_ON_ONCE(delalloc))
1046 return 0;
1047 if (WARN_ON_ONCE(unwritten))
1048 return 0;
1049
1050 return try_to_free_buffers(page);
1051 }
......
1827 const struct address_space_operations xfs_address_space_operations = {
1833 .releasepage = xfs_vm_releasepage,
對應 kernel 日志 kernel: WARNING: at fs/xfs/xfs_aops.c:1045 即可看出源文件 source/fs/xfs/xfs_aops.c 的 1045 行打印出了該堆棧信息, 實際上并沒有執行 try_to_free_buffers 就已經返回:
1045 if (WARN_ON_ONCE(delalloc))
1046 return 0;
WARN_ON_ONCE 則相對簡單, 在源文件 source/include/asm-generic/bug.h 即可找到:
73 #define __WARN() warn_slowpath_null(__FILE__, __LINE__)
85 #define WARN_ON(condition) ({ \
...
88 __WARN(); \
136 #define WARN_ON_ONCE(condition) ({ \
....
140 if (unlikely(__ret_warn_once)) \
141 if (WARN_ON(!__warned)) \
__WARN 函數則調用了堆棧信息里的 warn_slowpath_null 函數, 進而調用 warn_slowpath_common 函數打印了堆棧信息:
//source/kernel/panic.c
517 void warn_slowpath_null(const char *file, int line)
518 {
519 warn_slowpath_common(file, line, __builtin_return_address(0),
520 TAINT_WARN, NULL);
521 }
463 static void warn_slowpath_common(const char *file, int line, void *caller,
464 unsigned taint, struct slowpath_args *args)
465 {
466 disable_trace_on_warning();
467
468 printk(KERN_WARNING "------------[ cut here ]------------\n");
469 printk(KERN_WARNING "WARNING: at %s:%d %pS()\n", file, line, caller);
470
471 if (args)
472 vprintk(args->fmt, args->args);
......
485 print_modules();
486 dump_stack();
487 print_oops_end_marker();
我們大致可以看出這個堆棧信息只是警告, 和紅帽知識庫中描述的一致, 并不影響主機的使用.
總結說明
從上面源文件的函數來看, 只要 kswapd 內存回收的時候調用了 xfs_vm_releasepage 就有可能打印堆棧信息, 如果打印堆棧則不會執行 try_to_free_buffers 操作, 所以查看內存使用的時候可用內存并沒有增加. 如果不希望出現堆棧信息可以開啟 disable_trace_on_warning 函數對應的 kernel.traceoff_on_warning 內核參數關閉堆棧提示, 不過關閉后其他的內核信息也就不會再打印, 所以從這方面來看只有升級內核版本才會避免出現這個信息.
好了，以上就是這篇文章的全部內容了，希望本文的內容對大家的學習或者工作具有一定的參考學習價值，謝謝大家對腳本之家的支持。
